Control of heat produced during ATP hydrolysis by the sarcoplasmic reticulum Ca(2+)-ATPase in the absence of a Ca2+ gradient.
The amount of heat produced during the hydrolysis of ATP by the sarcoplasmic reticulum Ca(2+)-ATPase was found to vary depending on the Ca2+ concentration in the medium. When the CaCl2 concentration is raised from 0.1 to 2.0 mM a part of the energy derived from ATP hydrolysis is not dissipated as heat but it is used by the enzyme to resenthesize a small fraction of the ATP previously cleaved. Thus, Ca2+ seems to regulate the ATPase in such a way as to vary the fraction of energy derived from ATP hydrolysis which is converted into heat and that which is conserved as chemical energy.
de Meis
L
L
Departamento de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Brasil. demeis@server.bioqmed.ufrj.br
D000255:Adenosine Triphosphate / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D004734:Energy Metabolism; D006358:Hot Temperature; D006868:Hydrolysis; D018482:Muscle, Skeletal / Q000502:physiology; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology* / Q000378:metabolism
D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium